Mining drill



Jan. 7,

F. W. THURSTON I' MINING A:15mn

original" "'Fieaf April v2:5, 1925 e] Romand Y binding or locking together of the parts.

' provide a drill composed of separable screW- Reissued Jan. 7*, 1930 FRED WL THURSTON, OF LOS ANGELES, CALIFORNIA MINING DRILL Original No. 1,642,183, dated September 13, 1927, Serial No. 25,401, iled April 23, 1925. Application for reissue led September 7, 1929. Serial No. 391,087.

This invention relates to drills which are tially maximum drilling efficiency with subadapted for drilling rock and the like; and stantiall minimum breakagepf the parts, more particularly to drills designed to be perand so t at a breakage when it occurs will orcnssively driven and rotated, and adapted for dinarily be in a zone where the damage to the deep drilling operations; but my improvedrill as a whole, the loss of steel and the cost ments may be employed in other types of of repair will be minimized. drills including those used for oil drilling and earth boring.

This invention has for its general object an improved construction and arrangement of parts which is particularly durable and eilicient, and is readily adapted to manufacturingr and drilling operations.

- acteristics of the main elements of the drill, such as the bit, drill rod and intermediate or coupling member, they are or may be such 3g 1are set it-rg in my reissued Patent No. 16,

,grante a 5 1925. Other objects )df this invention will in pa-rt Anotherv object is to provide a construction be hereinafter specifically pointed out and for drills composed of separable parts which in part obvious from the arrangementsand are rigidly articulated, possess ruggedness constructions here set forth. and wear-resisting qualities, and are designed The invention accordingly consists in the to be readily assembled and disassembleg; features(gfconstruction,cmbinatiolns pli eles ecial revision bein made against t e ments an arrangement o parts w ic will p p g b bg exemrlld ind the constrlctilon herein- Still another ob'ect is to rovide a drill a ter set ort ,an the sco e o t is a licahavin a detachabl bit or hed with a screw tion will appear in the applended claini threafed coupling part preferably having For amore complete understanding of the shock-absorbing constitution, characteristics nature and advantages of this invention referand capacit which is adapted rigidly to supence should be had to the following detailed port the detachable bit, description, which describes the best illus- A further obj ect of the improvements is to trative embodiments of this invention at presprovide a drill which is, in most cases of fracf ent known to me, taken in connection with the turc, capable of easy and economical repair. accompanying drawing in which:

A more specific object of this invention is t0 Fig, 1 Shows, in perspective, an assembled mining drill embod ino this invention and threaded sections with aform of thread which lCOmpI-ising a bit ,mg Fin md, and n interhas cliaracterlstlcs specifically adaptlng 1t to mediate or Coupling member from which w1thstand the eii'ects of the impacts iroin a thev are detachable. lrhogiglu ghlgeggfw Fig. 2 is a longitudinal section of the Same, form of screwthreads the parts may be readthoml Ifod benglParjly brflent algaltl ily disassembled after the drilling operation. l?? l it 151ml if 21mg: 1 Us, rg Hgd Every drill may ultimately encounter con- Se 0- HP ma 1 Y 0 filpnts an ,0h Anh, ditions causing breakage, and another object rod Sectlonsv au COPY' e Hf me Wlb edc of this invention is to provide asectional drilhfhf' fo? deel) ,Sectqnal d1'111 l'ng y construction whereby the breakage from 'per- F 1l 4 1S, *l Slmlla'w Showmg the manner cussive driving is mostlyvconiined to limited of4 more 0r less rellevmg the screw kthreads zones (in the coupling or near the extremivfrom excessive stress and shock, by providing ties ofthe rod or bit), so as to obtain substanthe drill rod' and bit with shoulders, ,which As to the desirable properties and chari abut against the ends of the coupling, and

` waste and lossin the use of mining drill steel,

due to the short life and fracture, in one place or another, of the drill as a whole, andalso 'of its principal elements-where it has been made in separable sections.

The average mining drill machine (percus-V sive type) used/'in connection with a standard inch and a quarter drill steel, delivers a 15- pound hammer blow at the rate of 2300 blows a minute, and the revolving of the drill steel caused by the machine when applied against the reverse resistance of the bit in the hole causes great locking:I pressure to take place in a drill of this invention. The screw threads necessary to practical sectional drill construction must stand up under the powerful. impacts or vibrations set up by the h ammer, and the substantially equal reactions therefrom, andsaid threads must also not become immovably interlocked but must disengage freely, so that they can he readily unscrewed and the parts of the drill easily separated after the drilling operation for readjustment, or for resharpening and repair. Also, the screw threads must be so shaped as not to cause or aid the fracturing of any of the drill-sections, and I encountered great diiliculties with former shapesof threads until I arrived at the present invention.

Prolonged and intensive study of the great variety of conditions-involved in the'problem of producing' a more practically economical mining drill, accompanied by nu merous practical experiments, led to .the improvement set forth in my ypatent herein 4referred to, but the related subject of the best and most practicalconstruction of the screw threads (which I Ihave also discovered by said study and experiment) is not considered infsaid patent but is the subject of my present invention. According to this improvement the screw threads are ,sl/ibstantially smooth, continuously curved arid `rounded 'at all parts and especially at the concave or gutter parts of the thread. The convex or top portions of the screw threads should also, for the best results, be smoothly rounded and my invention does not exclude a semi-cylindrical formation of the extreme convex -portions or highest parts of the screw threads.

'I `he` thread is thus of what may be called a sinuous or undulatory contour continuously curved, in `cross section, both the deepest and highest parts of the threadbeing of a substantially semi-circular contour# but it is best t-o make said several vparts of the conf tour of a little less than a half circle so that a tangent line joining the outline of the lowest lart of the thread with the outline of the hlg est part of the thread will be a little Apling are usually formed by tapping. y periments have been conducted in casting a inclined (longitudinally) relative to the axis of the drill as a whole, thus retaining more metal and consequent strength, both in the couplings and`threaded' ends.

These threads may be formed on the steel by dies for cutting the same, or by forging or swaging them. The threads in the (uscrew threaded coupling part suitable in strength and otherwise for such a coupling member, and my invention does not exclude a coupling member so produced. It will further be understood that the threads could be deeper than above described and as shown in my drawings, and could have substantially the contour of a half circle for the convex part of the screw thread and of a half circle for the deepest part of the screw thread, in which case the ,drill would function successfully, but in such deeper screw thread construction metal would be removed which could better be left in the rod to add to the general strength of the same. v

Referring now to the drawing, 10 denotes the bit or drill head which is separable from v but rigidly supported by the drill-rod 11. The drill-rod is not directly connected with the bit 10, but has an intermediate or coupling part of member 12, which is separable from the drill-rod proper.

In order that the bit -10 may be rigidly supportedby the drill-rod, the intermediate or coupling member 12 is designed for threaded engagement with both the bit 10 and the drill-rod 11. This is conveniently accomplished by an interior thread, as shown at v13, which is cut continuously in the same direction through the member 12, and engages with pilots or Shanks having screwthreads 14 and 15, respectively provided on the bit 10 and the drill-rod 11. The direction of the screw-threads is such that, when the drill is being rotated during the drilling operation, the drill rod, bit vand intermediate part tend to screw together more tightly. Usually the construction and operation of the percussive mechanism is such that a left hand thread is required for this purpose, but some machines require a right hand thread. In order that theY coupling 12 and the Shanks on which the threads 14 a'nd 15 are made shall be particularly resistant to fracture, the said screw threads 13, 14 and 15 are made of undulating or sinuous contour illustrated onr a mately the preferredmanner of forming the undulatory screw threads on the three (or more) sections ofthe drill. The line 27 shows the contour of the screw thread looking at the side thereof and 28 is the line in which are located the centers for the curves for one half -of the thread, the centers for the curves ofthe other half of the thread being in the line 29. The amount of metal saved for strengthening the sections, by thus somewhat flattening the curves ofthe screw threads, and each thread as a whole, is substantially indicated by the space between the lines 28 and 29.

The said screw threads are or may be relieved of more or less of the end thrust applied to the drill, usually by the percussive machine, by the abutment of the ends of the drill rod and bit against each other within the cou ling, as shown in Figs. 2 and 3, or by shou ders 16 and 7, formed on the bit and rod respectively w 1ch shoulders abut against the ends of the coupling (Fig. 4) with or without contact of the rod and bit Shanks lwith each other.

The turning of the drill by the machine, occurring after each percussion, causes the said threaded ends to screw inward towards each other, or tend to do so. This effects considerable pressure of said ends against each other (Figs. 2 and 3) or against the coupling by means of the shoulders 16, 17 (Fig. 4). It results from this that the outer/faces of the threads 14 and 15 are strongly pressed against the inner' faces of the thread 13 of the coupling. This pressure is somewhat relieved by the percussion, but is very greatly augmented by the reaction from such percussion, and has a strong tendency by, repeated shocks recurring about 2300'times in a minute) to disrupt the coupling. It is therefore of great importance that this coupling be formed and tempered tohave shock-absorbingproperties, as

herein set forth, and that the threads be formed as embodied in this inyention in order that they may withstand in service ,under the foregoing mentioned conditions.

The length of the threads on the ends or stems of the bits and inthe cou lings, as shown inrFig. 4, when the ends of the steel abut in the coupling, are preferably made of su'licient length so that when the coupling part is screwed clear up tothe end of the thread .on the rods, the end of the rod will .extend for a distance of about half way through the coupling. Therefore, where the outer ends of the threads taper out on to the drill rod it forms a wedgingstop at 30, with.

-will go." Provision is made to have the opposite "threaded bit end whichfengages the coupling. long enough so that whenit has been.

screwed clear into the coupling to the point f of abutment, it will wnot engage the tapered' end of the thread 14, which might' cause too much tightening tendency. One end or-the other is desired to be relatively .free for unscrewing. the coupling remain tight on the drill rod "so as not to be turned when the bit is removed,

Iwhich is done more frequently than the removal of the coupling from the drill rod."

This is shown in the assembled drawing Fig. 1, the extra threads `being shown extending beyond the end of the coupling at the bit end On the otherhand where the shoulders are used, the coupling is screwed clear up to" the vshoulders and is stopped by abutting thereon.

Theoretically, it is Adesirable that thethreaded ends meet at a point about the middle of the coupling member. However, this `invention isnot limited to this and may vary therefrom somewhat, and "considering the factthat when the short types of bits are used and the same are discarded after becoming dull, it is desirable to have their stems as short as practicable, in 4which case the screw threaded end of the1bit may enter the cou,

" pling for a less distance than half way there- Ordinarily it is preferable to have i forced during the drilling operation, to

cool the bit and assist in the removal of particles of rock and the like resulting from the drilling.` The bit may have anyA desired and suitable form, a cruciform bit being illustrated.' I

The drill may be. greatly lengthened for deep drilling, as shown in Fig. 3, b the use of the required number of drill ro sections coupled to form a single long'drill byV a corresponding number of members 12. The long type of bit (Fig. 4) is adapted to berepeatedf ly resharpened by means of'forging in' the modern type of -drill sharpening machine. The short type (Figs. v1, 2 and 3) is meant to be used in service until dull, then reground only, and used as many times as possible,v at the end ofwhich time it is discarded' fora new one. The short bit is commonly referred to as the throw-away type 'of bit which 'is subject to no re-for ing, or heat-treatin process, and the long blt is commonly referre type of bit may now bepreferred in mining where there are present facilities for re-forging, heat treating, etc., while theshort type "of bit will ultimately do away with the expensive necessity of forging and heat treat-.

ing bits at the mine, thus ,effecting greater economles.

to as the re-forging type of bit. The longer cordingly the sai The undulating or sinuous form of screw thread, as shown herein or of equivalent form, results in advantages of material value. In brief, 'the described form .of screw threads, on the stems of the drill rod and bit and within the coupling member, enables said parts to live and function under stresses and shocks which would otherwise strain and fracture one or the 'other of thesaid parts, and consequently adds to the practical life of the drill; and enables the drill parts or sections to be readily separated ,andenables the stems of the rod and bit to be re-'theaded (when fractured) at decreased cost of time and 1abor; and materially aids in the much desired result of reducin v d screw threads are curved suiciently to accomplish the above results.

In order to give an anti-fatigue property and characteristic to the drill rodand a wear resisting property and characteristic to the `bit, and a shock absorbing property and characteristic to the intermediate or coupling member, the followingr procedure is suitable, and preferable according to my present best information: Y

Regarding the method of heat treatilig'the drill rod as herein shown, in order to gain the aforementtioned results, it has-been found, where the same is constructed of a suitable analysis, that the required process of its manufacture, the heating temperatures necessarily used in connection therewith, and thel .working, molding, rolling, etc., to which the steel is subjected' in forming the rod, especially in the hollow manner, as shown 'in the drawings, imparts' to it desirable qualities r for per orming its particular function in the V drill constructionv as a whole.

However, additional heat treating may be applied to the rod after same is put through the manufacturing process, with increased desirable results, inl substantially the following 'manner Ferca-When the drill rod is made of a. vanadiumsteel, and after the manufacturing and forming process is completed, same'may then Abe placed in a suitable furnace, having a heating temperature of 1550 degrees F., wherein it may be left for a period 0f about 30 minutes, same is then removedv and im mersed in a suitable, prepared quenching oil Ymixture, which is easily obtainable for quenching purposes. After the rod is cooled off' in the oil quench, same is theny placed i a suitable furnace, having a heating temper. ature of 1100 degrees F., for dpurposes of drawing and tempering, wherein it may be left for a period of 80 to 45 minutes.V It may, ifit is found more convenient instead, be immersed in a suitable melted salt solution, having a maintai ed temperature of 1100 degrecs F., for th same drawing purpose.

- When removed from the drawing process,

itis ready for service. Where other alloys the cost of mining. Ac-

be followed,.as given in the preceding paragraph, marked First, with very desirable results, except however, it has been found that .the heating' temperatures used may be as follows, instead of those mentioned above: The first heating temperature may be at a 1525 degrees F., and the drawing temperature at 550 degrees F.

As to the treatment of the bit:

The bit 10, as shown in the drawing, and

formed of chrome vanadium steel is placed in a suitable furnace, preferably gas-tired, having a heating temperature of 15250 F., and is left therein at that temperature for a period of 30 to 45 minutes.

immediately in a bath of suitably prepared quenching oil, which may be of a viscosity of 100 to 130 seconds at 100o F. When so.

quenched, the part is then preferably immersed in a drawing bath, which may be composed of a suitable melted salt solution, llaving a heating temperature of 1250 F., or a similarly heated furnace maybe used for'this purpose, in connection with a suitable packing material, the part being left therein, at that maintained temperature, for a period of 45 minutes. After that lapse of time, it is removed therefrom, and the cutting end of The part is "then removed from the furnace and placed the bit is then reheated to a temperature of i `temperature of 1550 degrees F., and is left therein at that temperature the same being maintained for a perlod of 45 minutes. The part is then removed from the furnace and laced immediately in a suitably preferred P P bath of quenching oil, preferably of a viscosity of 100 to 130 seconds at 100 degrees F. When so quenched the part may then be immersed in a drawing bath, preferably composed of suitable melted salt solution, having a maintained heating temperature of 700 F., wherein it is left, at this maintained temperature, for a period of 45 minutes. After such time has elapsed, it is removed therefrom and is ready for service. Instead of a drawing bath, a similarly heated furnace may be used, in connection with a suitable packing material, and when other alloys are used in y forming the coupling'part, the degrees of heating temperature may be varied somewhat to suit.

It is not intended to imply that the foregoing various means of heating treating, nor the various specic alloys designated and pointed out, for the various parts of the drill, may be the only means of arriving atthe desired results, in imparting to the various parts the desired qualities'or characteristics, nor is it'intended that this invention be limited in that direction, as any suitable means which renders the desired results are acceptable, and intended to be entirelyL within the scope of my invention.

Asmany changes could be made in the above construction and many apparently Widely diierent embodiments of this invention could be made without departing from the scope thereof, itis intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in .a limiting sense.`

The screw threads of undulatory contour may be applied in any of the forms of rotary impact mining drilllset forth in my Letters Patent 1,477,855, granted Dec. 18, 1923, and in reissued Letters Patent1 thereof No. 16,061, granted May 5, 1925. l

It is also to be understood that the language used in the following claims is intended to cover all of the genericand specific features of the invention herein described, and all statements .of the scope of 'the invention which, as a matter of language, might be said to fall therebetween.

I havedescribed the mode (if-operation of the undulatory continuously curved screw thread, in preventin or lessening fractures intheA sections, to t e best of my present knowledge. Experiments in actual use lshow its undoubted usefulness for that purpose and in adding to the life of the drill, and probably it operates in ways not now understood to, effect .that result. y

What I claim is:

separable sections comprising a 'drill rod, a bit, and a coupling member provided .with an internal screw thread ofvundulatory, curved contour, said rod and bit havin ends formedv with external 'screw threads o similancoi'i tour ada ted to engage within the. screwV pling and its sections and coupling thread `o the coupling member. y v

2. 'A rotary impact mining drill composed of separable sections comprising a drill rod;l a bit, and a coupling member provided with an internal screw thread of undulatory and continuously lcurved contour, said rod and bit having ends abuttingv within the coupling member and formed with external screw threads ofv similar contour adapted lto engage 1. IAn impact mining drill composed of j within the screw member.

3. A rotary impact mining drill 'composed of separable sections comprising a drill rod, a bit, and, a coupling member provided with thread of the coupling an internal screw thread of undulatory and drill composedH curved contour, said rod sections and bit j having ends formed with external screw threads of similar contour adapted to engage within the screw thread of tlie coupling members.

J 5. A rotary impact mining` drill composed of separable sections comprising a drillrod,

a bit, and a coupling member having shock absorbing properties and provided with an internal screw thread ofy undulatory and continuously curved contour, said rod and bit having ends formed with external screw threads of similar contour adapted to engage within the screw thread of the coupling member.

6. A rotary impact mining drill composed of separable sections comprising a drill. rod having anti-fatigue properties, a bithaving wear-resisting properties, and a coupling member having shock-absorbing properties and provided `with an internal screw thread of undulatory and continuously curved contour, saidl rod and bit having ends formed with external screw threads of similar contour adapted to engage within the screw thread of the coupling member.

7. A rotary impact mining drill composed of separable sections comprising a drill rod, va bit, and a coupling member having shockabsorbing properties and provided with an ,internal screw thread of undulatory and continuously curved contour, said rod and bit having ends abutting within the coupling member and formed with external` screw threads of similar contour adapted to engage within the screw thread ofthe coupling member.

`8. A sectional mining drill having a cou-Y formed onits interiorwith-screw threads of smooth, continuously curved and undulatory contour, as described.

10. A sectional rotary impactmming drill of two or more sections having a plurality of its sections formed with' and united by screw threads of curved undulatory contour.

11. In a rotary impact mining drill of the 7 kind composed of separable sections, having 

